Natural gemstones bring colour to jewellery in a way no other material can, and each one carries the character of the place it formed. This guide explains the gemstones we offer, how they are treated to bring out their best, and how to choose and care for them.
What is a gemstone?
A gemstone is a mineral prized for its beauty, durability and rarity, then cut and polished for jewellery. Sapphire, emerald, topaz and amethyst are all minerals that formed naturally in the earth.
A few materials used in jewellery are organic rather than mineral. Pearls grow inside molluscs, for example. They are valued for the same reasons as gemstones and are often grouped with them, but they need slightly different care.
How gemstones form
Most gemstones form over millions of years, deep underground, as minerals crystallise under particular conditions of heat, pressure and chemistry. Tiny traces of other elements give each its colour. A trace of iron and titanium turns corundum into blue sapphire, while chromium makes the same mineral a red ruby.
Because conditions vary from place to place, no two natural stones are exactly alike. Small natural inclusions, slight colour zoning or a particular depth of colour are part of a gemstone’s character and a sign of its natural origin.
The gemstones in our collection
The table below lists the gemstones you will find in our jewellery, in birthstone order. Hardness is measured on the Mohs scale from 1 to 10, where diamond is 10; the higher the number, the better a stone resists scratches.
| Gemstone | Colour | Hardness (Mohs) | Birthstone | Usual treatment |
|---|---|---|---|---|
| Garnet (incl. rhodolite) | Red to purplish red | 7–7.5 | January | Usually none |
| Amethyst | Purple to soft lilac | 7 | February | Usually none |
| Aquamarine | Pale to sky blue | 7.5–8 | March | Often heated |
| Emerald | Green | 7.5–8 | May | Usually oiled |
| Moonstone | Soft white, blue or brown sheen | 6–6.5 | June | Usually none |
| Ruby | Red | 9 | July | Usually heated |
| Peridot | Olive to lime green | 6.5–7 | August | Usually none |
| Sapphire | Blue | 9 | September | Usually heated |
| Opal | Play of colour | 5.5–6.5 | October | Often set as a doublet |
| Citrine | Yellow to golden orange | 7 | November | Usually heated |
| Topaz | Blue, white or pink | 8 | November | Blue: irradiated and heated; pink: may be coated |
| Smoky quartz | Brown to grey | 7 | — | Sometimes irradiated |
| Green quartz | Pale green | 7 | — | Heated or irradiated |
| Chrome diopside | Deep forest green | 5.5–6 | — | Usually none |
The exact treatment of the stones in each piece is listed in that product’s Key Details.
Understanding gemstone treatments
Many natural gemstones are treated after mining to improve their colour or clarity. This has been accepted practice across the jewellery trade for generations, and a treated stone is still a natural gemstone. What matters is that the treatment is disclosed, so you know exactly what you are buying. We list it for every gem-set piece.
- Heating deepens or evens out colour, as in most sapphires, rubies and citrines. The result is permanent.
- Irradiation creates the blue of blue topaz and some quartz colours, usually followed by gentle heating. It is permanent and the stones are safe to wear.
- Oiling fills tiny surface-reaching fissures in emerald with a colourless oil to improve clarity. Over many years the oil can dry out, and it can be removed by harsh cleaning.
- Coating adds a thin surface layer of colour, as in some pink topaz. It can wear with time, so coated stones need the gentlest care.
Some stones are assembled rather than treated. An opal doublet is a thin slice of natural opal bonded to a darker backing, which strengthens the opal and intensifies its colour. We always describe a doublet as a doublet.
Pearls
Freshwater pearls are grown in freshwater mussels. A pearl forms as the mussel coats an irritant with layer upon layer of nacre, the same lustrous material that lines its shell. Freshwater pearls are cultured, meaning the process is started by a pearl farmer, but the pearl itself is grown entirely by the mussel.
Each pearl has its own shape and lustre. Round pearls are the classic choice, while drop-shaped and baroque pearls have a softer, more individual look. Pearls are the traditional birthstone for June, alongside moonstone.
Choosing a gemstone
Colour first. Colour is the main reason to choose a gemstone, so choose the one you love. A rich, even colour that is neither too dark nor too pale is usually the most prized.
Think about how it will be worn. For a ring worn every day, harder stones such as sapphire, ruby and topaz cope best with knocks. Softer stones such as opal, moonstone and pearl are lovely in earrings and pendants, where they are better protected.
Look at the cut and setting. A well-cut stone shows its colour evenly and catches the light. Secure claws or a protective rubover setting help a stone last.
Consider meaning. Birthstones, anniversary stones and favourite colours make a gemstone personal, which is often what makes it treasured.
Caring for gemstone jewellery
Most gemstones need only simple, gentle care.
- Everyday cleaning. Use warm water, a drop of mild washing-up liquid and a soft brush, then rinse and pat dry. This suits sapphire, ruby, topaz, garnet, amethyst, citrine and aquamarine.
- Emeralds, opals and coated stones. Wipe with a soft, slightly damp cloth only. Avoid soaking, steam and ultrasonic cleaners, which can remove oil or coating and damage opal.
- Pearls and moonstone. Put them on after perfume, hairspray and cosmetics, and wipe with a soft cloth after wearing. Never use chemical cleaners.
- Heat and light. Keep gemstones away from sudden temperature changes. Store pieces away from direct sunlight, which can fade some stones over time.
- Storage. Keep each piece separately in a soft pouch, so harder stones cannot scratch softer ones.
- Settings. Check claws and settings from time to time, and take rings off for gardening, cleaning or the gym.
The right gemstone is the one you love
A natural gemstone is chosen for its colour, its meaning and the way it makes you feel. Every gem-set piece we offer states its stones and their treatment clearly, so you can choose with confidence.
Explore gemstone jewellery in our Earrings, Neckwear, Dress Rings and Bracelets collections. For pieces set with diamonds, our Diamond Guide explains what to look for.